1. Field of the Invention
The present invention relates generally to image reading apparatuses and particularly to image reading apparatuses reading an original while transporting it.
2. Description of the Related Art
Conventionally digital copiers and similar image reading apparatuses employ a technique referred to as so-called “reading an original while passing the original.” More specifically, an original is transported relative to a fixed line sensor in a sub scanning direction orthogonal to the line sensor as the original is read.
Such image reading apparatus is provided with a transparent platen between the original and the line sensor to fix a position at which a transported original is read. The original reflects light which is in turn received via the platen by the line sensor.
As such, if dust, paper particles, flaws or other similar foreign matters (hereinafter generally referred to as “dust”) adhere on the platen's reading position, the line sensor will read the dust while reading a transported original. This provides an output image with noise in the form of a line in the sub scanning direction.
Japanese Laid-Open Patent Publication No. 2002-77584 discloses a technique for improving the image quality by replacing image data of a region where noise in the form of a line appears in the sub scanning direction with image data of regions adjacent to and located on respective sides of the region having the line noise.
However, the image data of the adjacent regions on respective sides of the noise region is not always similar to the image data of the noise region. For example, in the adjacent regions, an edge region could be present or the color could suddenly change. More specifically, it is supposed here that an original has two regions that are one region of red and the other region of black and a noise region is present in the red region near the boundary between the two regions. In this case, although the noise region should be corrected to red, the noise region could be corrected to black due to the presence of the adjacent black region.